Studies On Photocatalytic Performance For Hydrogen Production Basing ZnIn₂S₄ Solid Solution Under Visible Irradiation

Photocatalytic water splitting into hydrogen is considered a promising way to solve the energy shortage problem. Amongst, developing efficient photocatalysts is the key. As a ternary sulfide semiconductor, ZnIn₂S₄ exhibits some fascinating advantages, such as low toxicity, good crystallinity, and considerable chemical stability.But the photocatalytic activity of ZnIn₂S₄ itself is low; so in this article, different ZnIn₂S₄ morphologies and ZnIn₂S₄-based composite photocatalysts have been synthesized via hydrothermal method in order to improve the photocatalytic activity,and the photocatalytic mechanism were studied.The first part, a series of ZnIn₂S₄-based composite photocatalysts was synthesized by a simple hydrothermal transformation of the co-precipitation precursor obtained by using Na2 S as the sulfur source in the presence of In3+ ions and the different content of Zn2+ ions.The semiconductors were characterized by X-ray diffraction?XRD?, UV–visible absorption spectra?UV–vis?,scanning electron microscopy?SEM? and transmission electron microscopy?TEM?. It was found that In?OH?₃ is selectively assembled at the rims of ZnIn₂S₄ nanosheets. The as-prepared heterojunction with in-situ photodeposited Pt on In?OH?₃ as a cocatalyst displays high-efficient photocatalytic H2 evolution under visible irradiation, and the apparent quantum yield at 420 nm reaches 38.3 %,the cause for enhanced photocatalytic activity is that the construction of a heterojunction composite by two semiconductors can enhance the transfer and separation of the photoexcited carrier pairs in the interface of photocatalyst.In the second part, a series of ZnIn₂S₄ photocatalysts was synthesized via melamine?MA?-assisted hydrothermal method. These ZnIn₂S₄ products were characterized by X-ray diffraction?XRD?, UV–visible absorption spectra?UV–vis?, scanning electron microscopy?SEM? and infrared spectroscopy. And the photocatalytic activities of the in-situ photodeposition of Pt on ZnIn₂S₄ were evaluated by photocatalytic hydrogen production from water under visible-light irradiation. It was found that the photocatalytic activities of these ZnIn₂S₄ products first rises then falls with the with the amount of melamine increasing, and the higher photocatalytic activity of MA-assisted ZnIn₂S₄ photocatalysts as compared to the no-melamine–assisted ZnIn₂S₄ photocatalyst,which can be attributed to the higher diffusion of electron donors and hydrone in the specific morphologies of the pore structure of ZnIn₂S₄ products,and a larger band gap energy corresponds to a more powerful redox capability.